首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   77369篇
  免费   4470篇
  国内免费   33篇
林业   3514篇
农学   2583篇
基础科学   505篇
  9668篇
综合类   12080篇
农作物   2974篇
水产渔业   3991篇
畜牧兽医   40252篇
园艺   941篇
植物保护   5364篇
  2018年   1171篇
  2017年   1235篇
  2016年   1189篇
  2015年   989篇
  2014年   1217篇
  2013年   3014篇
  2012年   2226篇
  2011年   2594篇
  2010年   1709篇
  2009年   1763篇
  2008年   2589篇
  2007年   2468篇
  2006年   2262篇
  2005年   2173篇
  2004年   2023篇
  2003年   2138篇
  2002年   1954篇
  2001年   2310篇
  2000年   2284篇
  1999年   1808篇
  1998年   750篇
  1997年   798篇
  1996年   703篇
  1995年   887篇
  1994年   748篇
  1993年   747篇
  1992年   1519篇
  1991年   1652篇
  1990年   1627篇
  1989年   1627篇
  1988年   1507篇
  1987年   1476篇
  1986年   1545篇
  1985年   1462篇
  1984年   1277篇
  1983年   1075篇
  1982年   756篇
  1979年   1180篇
  1978年   895篇
  1977年   850篇
  1976年   807篇
  1975年   832篇
  1974年   1034篇
  1973年   1074篇
  1972年   1022篇
  1971年   956篇
  1970年   930篇
  1969年   914篇
  1968年   758篇
  1967年   852篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
51.
52.
American Journal of Potato Research -  相似文献   
53.
54.
55.
56.
57.
58.
COPYRIGHT     
  相似文献   
59.
The mean area and minimal diameter of 3 histochemically determined myofiber types (1, 2A, and 2B; myosin ATPase in acid buffer) were calculated in middle gluteal muscle biopsy specimens from 62 stallions, 47 Andalusians and 15 Arabians, ranging in age from 6 to 12 years. Fourteen Andalusians and 7 Arabians were untrained, and the remainder were actively endurance-trained. The 6-month training schedules involved walking, slow trotting, and cantering. Fourteen Andalusians were moderately endurance-trained, whereas the other 19 Andalusians and 8 Arabians were strongly endurance-trained. Significant differences were not recorded between untrained and endurance-trained Arabians with respect to the area (type 1, 3,194 +/- 869 microns 2 and 3,150 +/- 370 microns 2; type 2A, 3,819 +/- 890 microns 2 and 3,380 +/- 356 microns 2; and type 2B, 4,872 +/- 962 microns 2 and 4,417 +/- 646 microns 2) or minimal diameter (type 1, 52.2 +/- 7.4 microns and 52.8 +/- 3.1 microns; type 2A, 58.1 +/- 6.7 microns and 55.0 +/- 2.8 microns; and type 2B, 65.3 +/- 6.4 microns and 63.4 +/- 4.3 microns) of the 3 fiber types, nor between untrained and endurance-trained Andalusians with respect to the area (untrained, 3,990 +/- 690 microns 2; moderately endurance-trained, 3,882 +/- 347 microns 2; and strongly endurance-trained, 3,758 +/- 510 microns 2) and minimal diameter (untrained, 58.1 +/- 4.7 microns; moderately endurance-trained, 59.7 +/- 2.7 microns; and strongly endurance-trained, 58.7 +/- 4.5 microns) of 2A fibers.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
60.
Hyperchylomicronaemia was identified in a four-week-old Siamese kitten with lethargy, in-appetence, hindlimb ataxia and profound anaemia. The kitten was euthanased and at necropsy a thrombus was found occluding the caudal aorta. Two littermates later presented with lethargy, inappetence and hypertriglyceri-daemia which resolved after being weaned on to a low fat diet. A similar condition was subsequently diagnosed in a kitten born to the same sire but a different queen. The expression of hyperchylomicronaemia in two related litters was suggestive of an inherited, familial defect in the function of lipoprotein lipase (LPL). The activity of this enzyme was reduced in all three parents, the two recovered cases and two related, but apparently unaffected kittens, compared with a control group of unrelated cats belonging to the breeder. This reduction in activity was not attributable to defective activation of LPL by its serum cofactor apolipoprotein C-II or the presence in plasma of a factor that inhibited LPL. The gene that codes for LPL was examined by restriction fragment length polymorphism analysis using a human LPL cDNA probe. The results showed that the cat has a similar, but not identical, LPL gene to man. However, there were no differences in the restriction fragment patterns obtained from affected, unaffected and control animals.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号